Vessel-based water injection systems

ABSTRACT

A marine vessel may be configured with a water pump and seawater treatment equipment for use in providing a marine vessel water pumping platform for pumping water into a subsea reservoir to help maintain or increase pressure to assist with producing oil and/or natural gas. The marine vessel water pumping platform allows for the pump and seawater treatment equipment to be continuously used for pumping operations as the marine vessel may be moved between subsea reservoir sites, which helps reduce maintenance costs. The water pump may be lower in minimal flow capacity than water pumps on platforms, thereby allowing for more diversity in supporting different oil and/or gas pumping in offshore drilling operations.

RELATED APPLICATIONS

This application claims priority to co-pending U.S. Provisional PatentApplication having Ser. No. 63/085,859 filed Sep. 30, 2020; the contentsof which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Deep sea or off-shore drilling is performed in many places around theglobe to extract oil and gas from subsea reservoirs. In offshoreproduction, platforms used to extract oil from the subsea reservoirsperform a number of functions in order to maintain the subsea reservoirin such a condition that oil and gas can be more easily extractedtherefrom. One such function of the platforms is to maintain pressurewithin the subsea reservoir by pumping processed seawater using a largewater pump on the platforms to a subsea injection manifold positioned onthe seabed. A conduit, such as a water injection riser, extends from theplatforms to the seabed and across the seabed to the manifold to enablethe water pump to pump the processed seawater into the subsea reservoir.Water pumps used on platforms typically output sufficient water toenable up to 100,000 barrels per day of water injection into the subseareservoir.

A few problems exist with current configurations and operations of theplatforms with maintaining pressure in the subsea reservoir. One suchproblem is the size of the hydraulic pumps on the platforms that aremeant for large production volumes (e.g., 100K barrels of oil productionper day). Another problem is that the cost of installing, moving, and/ormaintaining the water pumping infrastructure including the water pumpand water injection riser is very expensive and time consuming. As isunderstood in the art of offshore drilling, oil rigs are routinely movedand oil fields are also dynamic over time. For example, productionoperations vary for a variety of natural reasons (e.g., weather,seismic, pressure fluctuations, formation shifts, etc.) and manmadereasons (e.g., over-supply, under-supply, price fluctuations, politicaltensions, war, etc.), so subsea oil fields are routinely developed,slowed, or abandoned.

Moreover, because of the nature of subsea oil production, oil productionof a subsea reservoir from a platform may slow or stop altogether. Inthose events, equipment, such as the water pumps, risers, and otherequipment, may not be used for extended periods of time (e.g., weeks,months, years). Such stoppage can be harmful to the equipment and waterpumping infrastructure, including the water pump, water injection riser,subsea manifold, filters, fittings, and so forth.

As a result of routine non-operation of oil production by the platformsat subsea reservoirs due to natural and manmade reasons, maintenance isoften needed to ensure that all of the equipment and pumpinginfrastructure, including the water pumps, risers, seabed manifold,etc., properly work. The maintenance of off-shore drilling equipment forsubsea reservoirs is often expensive and time consuming. For at leastthese reasons, there is a need for an alternative solution to existingsystems and processes for maintaining subsea reservoirs that is lessexpensive to install and maintain, and that is more reliable forproducers that face oil and gas production variabilities to supportpumping water into subsea reservoirs to maintain pressure therein.

SUMMARY OF THE INVENTION

To provide for more reliable and cost effective pumping of treated waterinto a subsea or undersea reservoir so as to maintain or increasepressure therein, a marine vessel including a water pump configured topump treated seawater may be fluidly connected to a subsea injectionmanifold fluidly connected to the undersea reservoir. By using avessel-based water pump and seawater treatment equipment, if productiondisruption occurs at a subsea reservoir, the vessel may be repositionedto another subsea reservoir so as to continue to operate and avoidproblems that occur when water pumps and seawater treatment equipment isnot used for extended periods of time.

An adapter structure may be deployed in fluid communication between afirst conduit connected to the pump positioned on the marine vessel anda second fluid conduit connected to the manifold. The adapter structuremay be a water injection tree, and a second subsea injection manifold orsecond manifold may be connected thereto such that the second firstconduit may be connected to the second manifold. The first conduits maybe in the form of (i) drill pipe risers with a flexible jumper, (ii)coiled tubing risers with flexible jumpers, (iii) pipe riser that isflexible (i.e., flexible pipe riser), (iv) or otherwise. In operation,the marine vessel may be a single hulled marine vessel, and may beconfigured with a stationary positioning propulsion system to enable themarine vessel to remain positioned at the adapter. In being at theadapter, the marine vessel may be positioned above the adapter within arelatively near vertical alignment (e.g., within 50 feet or 100 feet).

In an alternative embodiment, rather than having the water pump andseawater treatment equipment positioned on a marine vessel, the waterpump and seawater treatment equipment may be positioned on a seabed nearthe subsea manifold. To power and/or control operation of the equipment,a marine vessel with power generation and control equipment may be usedto deliver power and control signals to the subsea water pump andseawater treatment equipment while positioned thereat. Still yet, thewater pump and seawater treatment equipment may be positioned on aseabed near the subsea manifold, and power and control equipmentpositioned on shore may be used to control the pump and equipment viasubsea power and control line cable(s). In this configuration, the risermay be eliminated as the vessel is providing power and control signalsto control subsea equipment. This configuration may (1) reduceinstallation time, (2) enable a smaller vessel to be used, (3) reducetime to recover cables and depart in advance of unanticipated weatherstorms, and/or (4) provide larger operating windows as only electricaldownlines may be connected to subsea equipment on the seafloor.

To provide for mobility, the water pump and water treatment equipmentmay be positioned on a structure (e.g., skid, floatable structure, orotherwise) that allows for the water pump and water treatment equipmentto be easily positioned on the seabed and moved. For example, a cranefrom a marine vessel may be used to lower and raise the equipmentpositioned on a skid depending on the configurations of the water pumpand water treatment equipment. It should be understood that one or moreskids may be utilized depending on the configurations of the water pumpand water treatment equipment. In an embodiment, floatation equipmentmay be positioned on the structure on which the water pump and watertreatment equipment is positioned so that an operator may inflate thefloatation equipment in order to raise the water pump and watertreatment equipment from the seabed, move the equipment from a firstmanifold, and lower the equipment in a new location to be at a secondsubsea manifold on the seabed, for example. In an embodiment, apropulsion system may be integrated with the structure to enable thestructure to rise or float above the seabed and move via remote control,semi-autonomously, or autonomously to a new location on the seabed.

One process for maintaining or increasing pressure in a subsea reservoircontaining oil and/or gas may include positioning a marine vesselincluding a pump configured to pump water to a subsea manifold in fluidcommunication with the subsea reservoir at the subsea manifold. Seawatermay be treated by seawater treatment equipment to produce treatedseawater in preparation for pumping the treated seawater into the subseareservoir. The pump may pump the treated seawater through one or moreconduits in fluid communication with the subsea manifold to cause fluidpressure in the subsea reservoir to be maintained or increased.

One embodiment of a system for maintaining or increasing pressure in asubsea reservoir containing oil and/or gas may include a marine vesselwith a pump disposed on the marine vessel that is configured to pumpwater to a subsea manifold in fluid communication with the subseareservoir. Seawater treatment equipment may be configured to producetreated seawater in preparation for pumping the treated seawater intothe subsea reservoir. One or more conduits may be in fluid communicationwith the pump and subsea manifold to enable the treated seawater to bepumped therethrough by the pump to cause fluid pressure in the subseareservoir to be maintained or increased.

One process for maintaining or increasing pressure in a subsea reservoircontaining oil and/or gas may include positioning a pump on a seabed,where the pump is configured to pump water to a subsea manifold in fluidcommunication with the subsea reservoir. Seawater treatment equipmentmay also be positioned on the seabed and be configured to producetreated seawater in preparation for the pump to pump the treatedseawater into the subsea manifold to the subsea reservoir on the seabed.The pump and seawater treatment equipment may be fluidly connectedtogether. The pump may be fluidly connected to the subsea manifoldthrough one or more conduits. A marine vessel including an electricpower generator and controller may be positioned at the pump andseawater treatment equipment (e.g., on the water surface thereabove).The electric power generator and controller may be electricallyconnected to the pump. Seawater may be treated by the seawater treatmentequipment to produce treated seawater in preparation for the pump topump the treated seawater into the subsea reservoir. The pump may pumpthe treated seawater through the one or more conduits in fluidcommunication with the subsea manifold to cause fluid pressure in thesubsea reservoir to be maintained or increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present invention are described indetail below with reference to the attached drawing figures, which areincorporated by reference herein and wherein:

FIGS. 1A-1C are illustrations of a subsea reservoir site with a marinevessel configured with a water pump and water treatment equipment forpumping treated water from the marine vessel to a subsea manifold forpumping into a subsea reservoir with oil and/or natural gas to maintainor increase pressure for producing the oil and/or natural gas by aplatform;

FIG. 2 is an illustration of two subsea reservoir sites in which amarine vessel configured with a water pump and water treatment equipmentfor pumping treated water from the marine vessel is moved from a firstsubsea reservoir site to a second subsea reservoir site; and

FIG. 3 is an illustration of a subsea reservoir site in which a subseawater pump and water treatment equipment may be deployed on the seabedand fluidly connected to a subsea manifold that is in fluid connectionwith a subsea reservoir, and a marine vessel with an electric generatorand controller for powering and controlling the subsea pump and watertreatment equipment.

DETAILED DESCRIPTION OF THE INVENTION

With regard to FIG. 1A, an illustration of an illustrative scene 100 aof a region in which off-shore production is taking place at a platform102 at a subsea reservoir (not shown) including oil and/or gas beneath aseabed 104. A subsea manifold 106 is shown to be positioned on theseabed 104 and is in fluid connection with the subsea reservoir. Theplatform 102 may include a water pump (not shown) and water treatmentequipment (not shown) positioned thereon (not shown). Typically, thewater pump would be in fluid communication with the subsea manifold 106via a water injection riser (not shown), as understood in the art, thatextends vertically to the seabed 104 and across the seabed 104 toconnect to the subsea manifold 106. However, in accordance with theprinciples described herein, the water pump and water treatmentequipment may be eliminated and replaced by a marine-vessel based waterpump or subsea water pump. As understood, the water pump typicallypositioned on the platform 102 is configured to pump treated water fromthe platform 102 to the subsea manifold 106 for injection into thesubsea reservoir. As understood in the art, the water pump on platform102 is configured for large volume pumping, such as 100K barrels per dayor more.

As an alternative and/or in addition to utilizing a water pumppositioned on the platform 102, a marine vessel 110 that includes awater pump 112 and water treatment equipment 114 positioned on themarine vessel 110 may be utilized. The water pump 112 may be configuredto pump lower volumes, such as 30K barrels/day, than the water pump onthe platform 102. By utilizing a lower volume pump, smaller sized subseareservoirs and/or lower desired pump volumes may be serviced by themarine vessel 110. The water pump 112 and water treatment equipment 114may be fluidly connected to one another on the marine vessel 110. Thewater treatment equipment 114 may be configured with filters to removeshells, sand, algae, and other impurities that is pumped into the watertreatment equipment 114. In addition, the water treatment equipment 114may deoxygenate the seawater to avoid corrosion and bacteria growth.Other water treatment processes may be utilized, as well.

As further shown, a water injection tree 116 may be positioned on theseabed 104 and be fluidly connected to the subsea manifold 106 by aconduit 118. In an embodiment, a subsea injection manifold 120 may beconnected to or in fluid connection with the water injection tree 116.In an embodiment, the water pump may be in fluid connection with thewater injection tree 116 via the subsea injection manifold 120 by adrill pipe riser 122 and flexible jumper 124. It should be understoodthat additional fittings and conduits not specifically shown may beutilized.

With regard to FIG. 1B, an illustration of an illustrative scene 100 bof a region in which off-shore production including oil and/or gasbeneath the seabed 104 is taking place via the platform 102 at thesubsea reservoir (not shown). In this embodiment, the marine vessel 110with the water pump 112 and water treatment equipment 114 may be fluidlyconnected to the water injection tree 116 via at least one coolingtubing riser 126 and flexible jumper(s) 128. As shown, the coiled tubingriser(s) 126 and flexible jumper(s) 128 may fluidly connect to thesubsea injection manifold 120.

With regard to FIG. 1C, an illustration of an illustrative scene 100 cof a region in which off-shore production is taking place via theplatform 102 at the subsea reservoir (not shown) including oil and/orgas beneath the seabed 104. In this embodiment, the marine vessel 110with the water pump 112 and water treatment equipment 114 may be fluidlyconnected to the water injection tree 116 via at least one flexible piperiser 130, such as a Magma pipe riser, that has at least a flexibleportion.

In operation, the marine vessel 110 may be configured with a propulsioncontroller and propulsion system that performs dynamic positioning tomaintain the marine vessel 110 in a substantially stationary position(e.g., within 3 feet). Stationary positioning the marine vessel 110 maybe performed by using a global positioning system (GPS) and/or localpositioning system (e.g., relative to a fixed structure or land marker),for example, that uses wireless RF communications or opticalcommunications, for example. Still yet, the propulsion controller may beconfigured to utilize various sensor data, including gyro rotational,accelerometers, and so forth, and provide automatic feedback to causethrusters to be maintained in a substantially fixed position. Althoughone marine vessel 110 is shown, it should be understood that multiplemarine vessels with a water pump and water treatment equipment that arefluidly connected to the water connection tree 116 may be utilizedduring pumping operation.

With regard to FIG. 2, an illustration of scenes 200 of multiple subseareservoir sites #1 and #2 is shown. In the scenes 200, two differentplatforms 202 a and 202 b (collectively 202) are shown to be pumping oiland/or natural gas at each of the different subsea reservoir sites fromthe subsea reservoirs. Seabeds 204 a and 204 b may have subsea manifolds206 a and 206 b positioned thereon that are in fluid connection with thesubsea reservoirs. As previously described, water injection risers hadhistorically been used by pumps and sea water treatment equipment onoff-shore platforms 202 to fluidly connect the water pumps with thesubsea manifolds 206 a and 206 b. However, by using marine vessel-basedwater pumps and/or seawater treatment systems, the cost of using largewater pumps on the platforms 202 a and 202 b may be avoided.

As shown, a marine vessel 210 that includes a water pump 212 and watertreatment equipment 214 may in a first instance connect to a first waterinjection tree 216 a that is in fluid connection with the subseamanifold 206 a via a first conduit 218 a. In an embodiment, the waterpump 212 may be in fluid connection with a subsea injection manifold 220a in fluid connection with the water injection tree 216 a via a conduit,in this case drill pipe riser 222 a and flexible jumper 224 a. Aspreviously provided, alternative conduits may be utilized. Because thewater pump 212 and water treatment equipment 214 are marinevessel-based, in the event that the first platform 202 a is shut downfor maintenance or the subsea reservoir having a problem or simply beingdiscontinued from being pumped, the marine vessel 210 may bedisconnected from the subsea injection manifold 220 a and/or drill piperiser 222 a and flexible jumper 224 a, and moved from the subseareservoir site #1 to the subsea reservoir site #2. The water pump 212may thereby be fluidly connected to the subsea manifold 206 b via waterinjection tree 216 b, conduit 218 b, and subsea injection manifold 220 bvia a drill pipe riser 222 a and/or flexible jumper 224 b. The use ofthe marine vessel based water pump 212 and water treatment equipment 214allows for lower cost operations since platform-based water pumps thatare more expensive for operation and maintenance are no longer needed.

One embodiment of a method for maintaining or increasing pressure in asubsea reservoir containing oil and/or gas may include positioning amarine vessel including a pump configured to pump water to a subseamanifold in fluid communication with the subsea reservoir at the subseamanifold. Seawater may be treated by seawater treatment equipment toproduce treated seawater in preparation for pumping the treated seawaterinto the subsea reservoir. The pump may pump the treated seawaterthrough one or more conduits in fluid communication with the subseamanifold to cause fluid pressure in the subsea reservoir to bemaintained or increased.

Positioning the marine vessel may include dynamically positioning themarine vessel in a substantially fixed location (e.g., maintained within3 feet). The process may further include fluidly connecting a waterconduit injection tree to the subsea manifold in fluid connection withthe subsea reservoir, and fluidly connecting a conduit between the waterinjection pump and the water conduit injection tree. In an embodiment,the process may include disconnecting the water conduit injection treefrom the subsea manifold, and fluidly connecting the conduit between thepump and a second subsea manifold in fluid connection with a secondsubsea reservoir. That is, the marine vessel moves to a different subseareservoir so the water pump and conduit is transferred from a first to asecond subsea manifold and equipment connecting thereto.

In an embodiment, fluidly connecting a conduit may include fluidlyconnecting a drill pipe riser and flexible jumper. Alternatively,fluidly connecting a conduit may include fluidly connecting at least onepair of a coiled tubing riser and flexible jumper. Still yet, fluidlyconnecting a conduit may include fluidly connecting a flexible piperiser.

With regard to FIG. 3, an illustration of an illustrative scene 300 of aregion in which off-shore production is being performed by a platform302 at a subsea reservoir (not shown) including oil and/or gas beneath aseabed 304. A subsea manifold 306 is shown to be positioned on theseabed 304 and is in fluid connection with the subsea reservoir. Theplatform 302 may include a water pump (not shown) and water treatmentequipment (not shown) positioned thereon. The water pump may be in fluidcommunication with the subsea manifold 306 via a water injection riser308 that extends vertically to the seabed 304 and across the seabed 304to connect to the subsea manifold 306. As understood, the water pumppositioned on the platform 302 is configured to pump water treated waterfrom the platform 302 to the subsea manifold 306 for injection into thesubsea reservoir.

In this embodiment, rather than a marine vessel 310 including a waterpump and water treatment equipment as presented in FIGS. 1A-1C, a subseawater pump 312 and optionally water treatment equipment 313 may bepositioned on the seabed 304 for use in pumping treated water. Thesubsea water pump 312 may be configured to pump lower volumes, such as30K barrels/day, than the water pump on the platform 302. By utilizing alower volume pump, smaller sized subsea reservoirs and/or lower desiredpump volumes may be serviced by the marine vessel 310. It should beunderstood that multiple water pumps may be positioned on the seabed 304in series or in parallel with respect to the subsea manifold 306. Thewater pump 312 and water treatment equipment 313 may be directly orindirectly fluidly connected to one another.

To power the subsea water pump 312, an electricity power generator andcontroller 314 may be positioned on the marine vessel 310. The generatorand controller 314 may be configured using any means to generateelectricity, including burning natural gas, solar power, or any other“green” or “non-green” electricity production system, as understood inthe art, and generate control signals for controlling operation of thesubsea water pump 312. A power line or cable 315 may be electricallyconnected to the generator 314 and extended from the marine vessel 310down to the subsea water pump 312 to power and control the subsea waterpump 312. That is, electrical power may be applied to the subsea waterpump 312 and control signals may control operation of the water pump.The control signals may cause the pump to turn ON and OFF. In anembodiment, the controller may also be used to control different aspectsof the pump, such as controlling different pistons at different timingoffsets. Moreover, sensor signals from the pump and/or seawatertreatment equipment may be communicated back to the controller formonitoring and controlling the pump and treatment equipment.

As further shown, a water injection tree 316 may be positioned on theseabed 304 and be fluidly connected to the subsea manifold 306 by aconduit 318. In an embodiment, a subsea injection manifold 320 may beconnected to or in fluid connection with the water injection tree 316.In an embodiment, the subsea water pump 312 may be in fluid connectionwith the water injection tree 316 via the subsea injection manifold 320by a drill pipe riser 322. It should be understood that additionalfittings and conduits not specifically shown may be utilized.

In an embodiment, the subsea water pump 312 may be disposed on a skid324 that enables the subsea water pump 312 to be placed on the seabed304 along with providing a platform for a crane 326 on the marine vessel310 to raise and lower the subsea water pump 312. In an embodiment,seawater treatment equipment may be positioned on the same or differentskid 324 as the subsea water pump 312. In an embodiment, a ballastand/or inflatable flotation device 326 along with an air pump 328 may bemounted to the skid 324, for example, to enable the skid 324 and subseawater pump 312 to be more easily lifted and/or moved from one locationto another either below or above the surface of the water. In anembodiment, a propulsion system (e.g., motor, propeller(s), directionactuator(s), etc.) may be integrated with the structure to enable thestructure to rise or float above the seabed, optionally below thesurface of the water, and move via remote control, semi-autonomously, orautonomously to a new location on the seabed.

One embodiment of a method for maintaining or increasing pressure in asubsea reservoir containing oil and/or gas may include positioning apump configured to pump water to a subsea manifold in fluidcommunication with the subsea reservoir on a seabed. Seawater treatmentequipment configured to produce treated seawater in preparation for thepump to pump the treated seawater into the subsea manifold to the subseareservoir on the seabed may be positioned. The pump and seawatertreatment equipment may be fluidly connected together. The pump may befluidly connected to the subsea manifold through one or more conduits. Amarine vessel including an electric power generator may be positioned atthe pump and seawater treatment equipment. The electric power generatormay be electrically connected to the pump. The seawater treatmentequipment may treat the seawater to produce treated seawater inpreparation for the pump to pump the treated seawater into the subseareservoir. The pump may pump the treated seawater through the one ormore conduits in fluid communication with the subsea manifold to causefluid pressure in the subsea reservoir to be maintained or increased.

In an embodiment, positioning the marine vessel includes dynamicallypositioning the marine vessel in a substantially fixed location. Theprocess may further include fluidly connecting a water injection tree tothe subsea manifold in fluid connection with the subsea reservoir, andfluidly connecting a conduit between the water injection pump and thewater injection tree.

The process may further include disconnecting the water conduitinjection tree from the subsea manifold, and fluidly connecting theconduit between the pump and a second subsea manifold in fluidconnection with a second subsea reservoir. The process may furtherinclude mounting the pump onto a skid for deployment to the seabed. Theskid may include dynamic flotation to assist raising, lowering, and/ormoving the pump and/or water treatment equipment.

While a marine vessel based water pump and water treatment equipmentsolution and seabed based water pump and water treatment equipmentsolution have been presented, it should be understood that alternativesolutions are possible. For example, the marine vessel is shown to be amanned marine vessel. However, it should be understood that an unmannedmarine vessel (e.g., drone marine vessel) may be utilized by using aremote control of the unmanned marine vessel, generator, localcontroller, water pump, and water treatment equipment. Unmanned marinevessels may include the same or similar controllers and propulsionsystems to maintain the unmanned marine vessel in substantiallystationary locations. Still yet, rather than using a marine vessel,power and control signals from land may be provided and remote controlof the subsea water pump and water treatment equipment may be provided.Other manned and unmanned configurations are possible along withalternative configurations of vessel-based, drone vessel-based, andsubsea water pump and/or water treatment equipment.

The previous description is of at least one embodiment for implementingthe invention, and the scope of the invention should not necessarily belimited by this description. The scope of the present invention isinstead defined by the following claims.

What is claimed is:
 1. A method for maintaining or increasing pressurein a subsea reservoir containing oil and/or gas, said method comprising:positioning a marine vessel including a pump configured to pump water toa subsea manifold in fluid communication with the subsea reservoir atthe subsea manifold; treating seawater by seawater treatment equipmentto produce treated seawater in preparation for pumping the treatedseawater into the subsea reservoir; and pumping, by the pump, thetreated seawater through one or more conduits in fluid communicationwith the subsea manifold to cause fluid pressure in the subsea reservoirto be maintained or increased.
 2. The method according to claim 1,wherein positioning the marine vessel includes dynamically positioningthe marine vessel in a substantially fixed location.
 3. The methodaccording to claim 1, further comprising: fluidly connecting a waterconduit injection tree to the subsea manifold in fluid connection withthe subsea reservoir; and fluidly connecting a conduit between the waterinjection pump and the water conduit injection tree.
 4. The methodaccording to claim 3, further comprising: disconnecting the waterconduit injection tree from the subsea manifold; and fluidly connectingthe conduit between the pump and a second subsea manifold in fluidconnection with a second subsea reservoir.
 5. The method according toclaim 1, wherein fluidly connecting a conduit includes fluidlyconnecting a drill pipe riser and flexible jumper.
 6. The methodaccording to claim 1, wherein fluidly connecting a conduit includesfluidly connecting at least one pair of a coiled tubing riser andflexible jumper.
 7. The method according to claim 1, wherein fluidlyconnecting a conduit includes fluidly connecting a flexible pipe riser.8. A system for maintaining or increasing pressure in a subsea reservoircontaining oil and/or gas, said system comprising: a marine vessel; apump disposed on the marine vessel and configured to pump water to asubsea manifold in fluid communication with the subsea reservoir;seawater treatment equipment configured to produce treated seawater inpreparation for pumping the treated seawater into the subsea reservoir;and one or more conduits in fluid communication with the pump and subseamanifold to enable the treated seawater to be pumped therethrough by thepump to cause fluid pressure in the subsea reservoir to be maintained orincreased.
 9. The system according to claim 8, wherein positioning themarine vessel includes a propulsion control system configured todynamically position the marine vessel in a substantially fixed locationwhen the pump is pumping the treated seawater.
 10. The system accordingto claim 8, further comprising: a water conduit injection treeconfigured to the subsea manifold in fluid connection with the subseareservoir; and a conduit fluidly connected between the water injectionpump and the water conduit injection tree.
 11. The system according toclaim 10, wherein: the conduit is fluidly disconnected from the pump andthe water conduit injection tree from the subsea manifold; and theconduit being fluidly connected between the pump and a second subseamanifold in fluid connection with a second subsea reservoir.
 12. Thesystem according to claim 8, wherein the conduit includes a drill piperiser and flexible jumper.
 13. The system according to claim 8, whereinthe conduit includes a drill pipe riser and flexible jumper.
 14. Thesystem according to claim 8, wherein the conduit includes at least onepair of a coiled tubing riser and flexible jumper.
 15. The systemaccording to claim 8, wherein the conduit includes a flexible piperiser.
 16. A method for maintaining or increasing pressure in a subseareservoir containing oil and/or gas, said method comprising: positioninga pump on a seabed, the pump configured to pump water to a subseamanifold in fluid communication with the subsea reservoir; positioningseawater treatment equipment on the seabed, the seawater treatmentequipment configured to produce treated seawater in preparation for thepump to pump the treated seawater into the subsea manifold to the subseareservoir; fluidly connecting the pump and seawater treatment equipmenttogether; fluidly connecting the pump to the subsea manifold through oneor more conduits; positioning a marine vessel including an electricpower generator at the pump and seawater treatment equipment;electrically connecting the electric power generator to the pump;treating seawater by the seawater treatment equipment to produce treatedseawater in preparation for the pump to pump the treated seawater intothe subsea reservoir; and pumping, by the pump, the treated seawaterthrough the one or more conduits in fluid communication with the subseamanifold to cause fluid pressure in the subsea reservoir to bemaintained or increased.
 17. The method according to claim 16, whereinpositioning the marine vessel includes dynamically positioning themarine vessel in a substantially fixed location.
 18. The methodaccording to claim 16, further comprising: fluidly connecting a waterinjection tree to the subsea manifold in fluid connection with thesubsea reservoir; and fluidly connecting a conduit between the waterinjection pump and the water injection tree.
 19. The method according toclaim 18, further comprising: disconnecting the water conduit injectiontree from the subsea manifold; and fluidly connecting the conduitbetween the pump and a second subsea manifold in fluid connection with asecond subsea reservoir.
 20. The method according to claim 16, furthercomprising mounting the pump onto a skid for deployment to the seabed.